Multiple clamp for lithographic plate graining machines



Dec. 28, 1948. G. DUNN 2,457,453

MULTIPLE CLAMP FOR LITHOGRAPHIC PLATE GRAINING MACHINES Filed Jan. 6, 1947 M m 9. N Ni 2 Sheets-Sheet l Dec. 28, 1948. M. G. DUNN MULTIPLE CLAMP FOR LITHOGRAPHIC PLATE GRAINING MACHINES 2 Shets-Sheet 2 Filed Jan.

1 I I P 1;??? Y) r 1"- 'IIIIIIIIIIIIIII]IIIIII/IIIIIIIIIIIIIIII/IIIII/IIIIII Patented Dec. 28, 1948 MULTIPLE CLAMP FOR LITHOGRAPHIC PLATE GRAINING MACHINES Martin G. Dunn. Washington, D. 0.

Application January 6, 1947, Serial No. 720,389

10 Claims.

This invention relates to improvements in lithographic plate graining machines, and more particularly to hold-down devices for clamping the plates firmly and evenly upon the bottom of the grainer box or tub.

The general object of the invention is to provide a novel and improved plate clamping device for graining machines by means of which the edges of a number of plates may be clamped in position for graining by pursuing a minimum of manual operations.

Another object of the invention is the provision of a novel multiple grainer clamp of the class described which can be quickly applied and released, which is resilient in operation, and which is easy to manufacture and install while at the same time being of sturdy construction and not liable to get out of order or to require frequent repair or relacement. v

In its preferred embodiments, the invention contemplates the provision of a plurality of spring pressed hold-down feet disposed in rows across the grainer tub and preferablyin alignment with the clamp-supporting cross bars which span the tub at intervals along the length thereof.

The T;

' line 4-4 of Figure 2; the released position of the clamping feet associated with one of the cross bars are all operativeiy connected with an elongated actuating bar or frame which is disposed for limited Vertical movement adjacent the cross bar, and manually operated levers are arranged to raise and lower the clamp supporting frames in order to release and apply the several clamps to the plates.

By means of this novel arrangement, .a plurality of clamps may be released and applied by the manipulation of one or two levers and the time Of operation of the grainin'g process much reduced.

Other objects and features of noveltywill be apparent from the following specification when read in connection with the accompanying drawings in which certain embodiments of the invention are illustrated by way of example.

In the drawings:

Figure l is a view in perspective of one end of the graining machine tub embodying the principles of the invention; 7 l

Figure 2 is a fragmentary vertical sectional view taken on line 2-2 of Figure 1, one of the presser feet or clamps being shown in raised or released position;

Figure 3 is a similar view showing the foot in depressed or operative clamping position;

Figure 4 is a fragmentary view in vertical sec- ,tion taken along the clamp bar approximately on r parts of the clamp, however, being shown in broken lines;

Figure 5 is a fragmentary perspective view of an end of the tub of a plate graining machine, showing another embodiment of the invention; and I Figure 6 is a fragmentary vertical sectional view taken approximately along the center line of the clamp bar assembly.

The grainer box or tub formin the basis of the embodiment illustrated in Figures 1 to 4 of the drawings is indicated in the drawings by the reference numeral l0, and it will be understood by those skilled in the art that the tub I!) is mounted in a substantially horizontal position for rotary or gyratory movement in the horizontal plane. Means are also provided for loading the tub, after the lithographic plates are properly clamped therein, with the steel balls or marbles and the wetted abrasive material, as is also well known in the art. The tub II] is provided with an end Wall H, side walls l2, and a bottom wall I3 upon which is secured the rubber blanket IS. A wooden strip I6 is secured along the inside of the lower portion of the side and end walls and to this strip is secured the marginal strip of rubber l1.

Lithographic plates 20 which are to be grained are laid in orderly rows upon the blanket l5 upon the bottom of the tub, and are adapted to be firmly retained in fiat position to be acted upon by the abrasive under the influence of the rolling balls or marbles. These plates are of any familiar type, whether made of zinc, copper, or aluminum, or whether new or used. The object of the graining process is to prepare clean grained surfaces on the plates for the reception of the lithographic image in the process of lithographic or offset printing, In the case of the treating of old plates, the object is to remove the old image from the surface of the plate so that the plate may be used over and over again.

Although the hold-down clamp may be applied directly to the corners or margins of the plates 20, it is preferred to cover the marginal edges of the plates with the hold-down strips 22 which are preferably made of thin flexible material and provided with bevelled or chamfered edges so that the balls may roll freely across their surfaces as Well as upon the working. surfaces of the plates being treated.

The clamping arrangement comprises generally a series of cross bars or frames 25 which span the vtubat intervals alongthe length thereof, and

edge of the side wall flange 28-o,f,thentub,and

serves to aid in guiding the adjusting movernent of the clamp frame. To the vertical flange of the angle piece 30 at each end of the-framais welded the projecting jaw plate, .3|.through an.

opening in which is threadedthe set screw 32.

It will be understood that the angle pieces 22 overlie the tub flange 25 and the flange is receivedbetween the angle pieces2 8 an d the overlying projeetion 3|, The set, screwor bolt. 32 serves to rigidly secure the clamp frame, to..the flange,2 6;in its adjusted position above the margins o f the plates 20in the tub.

Withinthe slot between. the flanges 2? ;of the angle irons 28, there are disposed at suitable intervals the clamps ;35.-each.of which. comprises a flat foot portion hich is adapted .to bear upon the plates'20 or the strips.22; andia .stem portion 31 wlnchextends through the slot between the flanges 28 Surrounding .eachotthe stems 31' is a coil spring 38 which is compressed between theedgesoi the flanges 29;.and acottenpin. 39 passingthrough. an openingin thestem-S'I. A washer.4, may be providedtoafiorda bettei' spr ing seat adjacent the, edgesoithe flanges". The spring 38 thus continually. urges .the clamp element 35" downwardly toward the plates. :To accommodate the clampingarrangement toplates of varyingdimensions, the clamps 35 :.may.be moved along the frame 25 to anydesired position.

In. order to .raise theclamps 35. from contact with, the, plates .28 or .the strip 22,. asforremoval of the finished plates and the positioning of new plates to be treatedg an. actuatingmeans isprovided. which includes, a pair of. spaced. angle irons 4.2 between the vertical flanges of which the upper endsof the stemsilltproiect. Arcotter .pin. 43

extends throughamopening in. the upper end of each stem 31 and bears uponthe upper edges. of the vertical flanges of theangles :42.- At two spaced. points .along.the angles 42 ipivotpins or bolts44 are provided. These pinspass through the verticaliflangesof the angles 42 and through alever arm 45. At appropriate pointsalong the frames 2.5,.bearing plates .41 are. provided, these plates being .securedas by .welding to' the under side of theflanges 29 of theangles 128w The plates .41 ere adapted to be contacted by the lower en s 18 of the levers .45., and..it..wili bereadily understood thatupon rocking the levers 45 the end 48 will bear upon and slidealong the plate 41 and the pin. willbe raised, thus. lifting the actuating subframecomprised by the angles 42.-

The lifting .of .this actuating. subwfrarne .42,

through the cotterpins 43, will lift each one of the clampelements 35,v..the principal parts of the device being shown inraised position, in broken lines, in Figure 40f the drawings. The angle irons 42. of thelifting frame are rigidly connected together adjacent their ends by theublocks .46 which serve to connectthein verticalfiangesi .Al-

though twp hand levers. 45 are provided itis. conceivable, that onediitinglever could .beprolvided at the center of the frame, although such an arrangement might not be as satisfactory the use of two levers.

An important feature of the lever arrangement is illustrated to best advantage in Figure 4 of the drawings. It will be noted that the spacing and dimensioning of th various parts, particularly the lever 45 and the stem 3? ol the clamps 35, is such that when the parts are in applied position, the levers 45 will contact both the plate 41 at 50 and the top of the stem 3] at 5|. In this way the weight of the adjusting SLlblllllll! is. utilized to. bear upon the presser clamps 35 when they are applied to the plates, and there is a minimum of lost motion between the operative "partstwhich would produce rattling during the vigorous oscillation of the tub.

In Figures E and 6 of the Clltl'l l'll illustrated another embodiment of in which a modified clamping frame Thev various parts or" the tub and p we arrangement will be given the same refer nce numerals the preced ing embodiment. 1e. alt native clamp supporting frame, however, c gnated generally by the reference numeral The relatively. fixed part of the clamp frame i25vcomprisesithe channel member E28 the of wh-ich rest upon the opposite side wall flanges 26; of the tub. Plates I25 are secured as by welding tothe under sides of the ends of the channels I28 and form a lower jaw for receiving the tub flange 26. A set screw I32 serves to fix thechannel {I28 inadjusted posit o along the tub. Openings I-are provided. thebas e flange of the channel I23 1? tion of thestems I3? of the presser the .c lampl35 adapted to bear upon Iithographieplates 29 or the hold-down strips The coil spring I38 surrounds each stern I31 and is seated at its upper and lowerends against thelower surface of the channel I28 and against the cotter pin. I35 respectively.

Thelifting subframe in this embodiment cornprises .the inverted channel I42 which fits within there is invention employed.

.the flangesof the base channel I28. Openings I4I arejormed-inthe basefiange of the channel I42 andregister with openings I30 in the channel Inland are adapted. toreceive the stems I31 of the,c1amps I35. Cotter pins I43 pass through theupper ends of-the stems I31 and bear upon the .topsurface of the operating channel bar I42. At one or two points along the channel I42 slots I46 are provided for the reception of the lower ends of the operating levers I45. Ears I52 are provided. at. each side of the slot I46 and a pivot pin or bolt I44 passes through registering openingsin ears I52 and in the lever I45.

The lower end I48 of the lever bears against the upper surface of the bottom flange of the channel "land is adapted tomove alongthis surface whenthe lever is swung to raise or lower the liftingframe. In Figure 6 of thedrawings the principal parts are shown in. solid lines in clamping position and in broken lines in released orraised position, and the operation of this form of. the invention will be readily understood therefrom. As a lever I45 is swung from its solid line position the pin I44 is raised and this causes the of the invention as defined by the following claims. 1

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In a lithographic plate graining machine, a grainer tub, an elongated clamp supporting frame secured to and extending across andabove the tub in spaced relation to the bottom thereof, a plurality of plate clamps carried by said frame, each of said clamps including a presser foot adapted to exert bearing pressure upon a plate resting upon the bottom of the tub, means for resiliently urging said feetdownwardly toward said plates, and means for simultaneously raising said clamps from and lowering them to clamping position.

2. In a lithographic plate graining machine, a grainer tub, an elongated clamp supporting frame secured to and extending across and above the tub in spaced relation to the bottom thereof, a plurality of plate clamps carried by said frame, each of said clamps including a presser foot adapted to exert bearing pressure upon a plate resting upon the bottom of the tub, means operatively engaging said feet and said supporting frame for resiliently urging said feet downwardly toward said planes, an elongated actuating subframe operatively connected with all of said clamps, and manual operating means for raising and lowering said sub-frame and thus the clamps which are connected thereto.

3. In a lithographic plate graining machine, a grainer tub. an elongated clamp supporting frame secured to and extending across and above the tub in spaced relation to the bottom thereof, a plurality of plate clamps carried by said frame, each of said clamps including a presser foot adapted to exert bearing pressure upon a plate resting upon the bottom of the tub, means operatively engaging said feet and said supporting frame for resiliently urging said feet downwardly toward said plates, an elongated actuating subframe operatively connected with all of said plate clamps, and means carried by said sub-frame adjacent each end thereof and operatively associated with said supporting frame and adapted to be simultaneously manually actuated to raise and lower said clamps.

4. In a lithographic plate graining machine, a grainer tub, a plate clamping assembly secured to said tub for adjustment along the tub and spanning the tub in spaced relation to the bottom thereof, said assembly comprising an elongated base frame, a plurality of vertically movable plate clamps, and a clamp actuating subframe; means for guiding said clamps past said base frame during their raising and lowering movements, connections between said sub-frame and each of said clamps, means whereby the subframe is raised and lowered relative to said base frame and the associated clamps moved from operative position to released position.

5. In a lithographic plate graining machine, a grainer tub, a plate clamping assembly secured to said tub and spanning the tub in spaced relation to the bottom thereof, said assembly comprising an elongated base frame, a plurality of vertically movable plate clamps each comprising a vertical stem and a presser foot, and a clamp actuating sub-frame; means for guiding said clamp stems past said base frame during their raising and lowering movement, resilient means which bear against said clamps and said base frame to urge the clamps downwardly toward plate clamping position, connections between said sub-frame and each of said clamps, and at least one lever operatively' connecting the sub-frame and said base frame.

6. In a lithographic plate graining machine, a grainer tub, a plate clamping assembly secured to said tub and spanning the tub in spaced relation to the bottom thereof, said assembly comprising an elongated base frame, a plurality of vertically movable plate clamps each comprising a vertical stem and a presser foot, and a clamp actuating subframe; means for guiding said clamp stems past said base frame during their raising and lowering movement, coil springs surrounding said stems and bearing against said clamps and said baseframe to urge the clamps downwardly toward plate clamping position, connections between said sub-frame and each of said clamps, and at least one lever pivoted to one of the frames and adapted to cam against the other frame whereby the sub-frame is raised and lowered relativeto said base frame and the associated clamps moved from operative position to released position.

'7, In a lithographic plate graining machine, a grainer tub, a plate clamping assembly secured to said tub and spanning the tub in spaced relation to thebottom thereof, said assembl comprising an elongated base frame; a plurality of vertically movable plate clamps each comprising a vertical stem and a presser foot, and a clamp actuating sub-frame; means for guiding said clamp stems past said base frame during their raisingand lowering movement, resilient means which bear against said clamps and said base frame to urge the clamps downwardly toward plate clamping position, connections between said sub-frame and each of said clamps, at least one lever operatively connecting the sub-frame and said base frame; said base frame comprising a pair of angle shapes spaced apart for the reception of the clamp stems therebetween, said sub-frames also comprising angle shapes spaced apart to receive the upper portions of said stems, mutual abutting portions on each stem and the sub frame for connecting said stems and said sub-frame at least during their upward movement, and pivot pins passing through said levers and said vertical flanges of the sub-frame, an end of each of said levers adapted to bear upon a surface of said base frame.

8. In a lithographic plate graining machine, a grainer tub, a plate clamping assembly secured to said tub and spanning the tub in spaced relation to the bottom thereof, said assembly comprising an elongated base frame, a plurality of vertically movable plate clamps each comprising a vertical stem and a presser foot, and a clamp actuating sub-frame; means for guiding said clamp stems past said base frame during their raising and lowering movement, resilient means which bear against said clamps and said base frame to urge the clamps downwardly toward plate clamping position, connections between said sub-frame and each of said clamps, at least one lever operatively connecting the sub-frame and said base frame; said base frame comprising a pair of angle shapes having vertical flanges and horizontal inwardly directed flanges spaced apart for the reception of the clamp stems therebetween, said sub-frames also comprising angle shapes having outwardly extending horizontal flanges and spaced adjacent vertical flanges spaced apart to receive the upper portions of said stems, stop elements for connecting said stems and said sub-frame at least during their upward movement, pivot pins passing through said levers and said vertical flanges of the sub-frame, an end of each of said levers adapted; to bear upon a surface of said base frame.

9. In a lithographic plate graining machine a graiuer tub, a plate clamping assembly; secured to saildrtub and spanning the tub in spaced relation to the bottom thereof, said assembly comprising anelongated base frame, a plurality of vertically mnvable plate clamps each comprising avertical stemand apresser foot, and a clamp actuating subeframe; means for guiding said clampstems past said base frame during their raising and lowering movement, resilient means which bear against said clamps and said base frame to urge the clamps downwardly toward plate clamping position, connections between said sub-frame and each of said clamps, at least onelever operatively connecting the sub-frame and said base frame; said-base frame comprising a pair of angle shapes having vertical flanges and horizontal. inwardly directed flanges spaced apart for the reception ofthe clamp stems therebetween, said sub-frames also comprising angle shapes having outwardly extending horizontal flanges and spaced adjacent vertical flanges spaced apart to receive the upper portlonsrof said stems, stop elements for connect: lngsaid stems-and said sub-frameat least during their i upward movement, pivot pins passing through said levers and said vertical flanges of the sub-frame, the parts being so constructed and arranged that when in lowered operative position, the lquterlmanipulative portion of thelever bears upon thevupper end of an adjacentlclamp stem,

while the-lower end bears againsta camming S111:-

face .of thebase frame, and thus causes the weight of -thesub-frame and levers to assist in exertingdownward force upon the clamps, and minimizes lostmotion and rattling during opera anon.

10. In a lithographic plate graining machine a grainertub, a plate clamping assembly secured to said tub'and-spanning the tub in spaced relation to the bottom thereof, said assembly comprising an elongated base frame, a plurality of vertically movablelplate clamps each comprising a vertical stem and a presser foot, and a clamp actuating sub-frame; means for guiding said clamp stems past said base frame during their raising and lowering movement, resilient means which bear againstsaid clamps and said base frame to urge the clamps downwardly toward plate clamping position, connections between said sub-frame and each of said clamps, at least one lever operatively connecting the sub-frame and said base frame; said base frame comprising a channel bar having openings at intervals in its web for the reception of the .clamp stems, said sub-frame comprising an inverted channel adapted to be received within the flanges of the channel forming the base frame when in'lowe-red position, openings in the web of saidsub-frame through which the upper ends of the clamp stems extend, stop means carried by the upper end ofsaid stems for operatively connecting them to. said sub-frame, one or more openings in the web of said sub-frame to accommodate an operating lever and means for pivoting said lever ,to said sub-frame adjacent an opening, one end of said lever adapted to cam against theweb of said base frame when. actuated, the opposite end of the lever adapted for manual actuation.

MARTIN G. DUNN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,925,963 Huck Sept. 5, 1933 1,935,306 Zorkin u Nov. 14. 1923 1,199,028 Cornwall Sept. 19, 1916 

